The present invention relates to the art of combustion heating, and more particularly relates to a burner for use in a heat regenerator system.
Many large and small industrial and commercial furnaces throughout the world burn fossil fuels such as coke oven gas, natural gas, propane, butane or fuel oil. Some of the furnaces (known as "direct fired" furnaces) heat the furnace load by applying the products of combustion (POC) directly to the load. Other furnaces (known as "radiant tube" furnaces) confine the POC within ceramic or alloy tubes. The tubes transmit the heat of the POC to the furnace load, but isolate the load from direct contact with the POC.
The majority of these furnaces were designed more than one decade ago, at a time when the cost of fossil fuels was relatively low. The cost of fossil fuels has increased tremendously since then. Not surprisingly, the current high cost of fossil fuels has aroused substantial interest in methods of improving the fuel efficiency of existing fossil fuel fired furnaces. To be commercially feasible, a method of improving the efficiency of the combustion process must conform to the space and power requirements of the existing installation, and should involve the replacement of as little of the existing equipment as possible. Unfortunately, most known processes for improving the fuel efficiency of combustion furnaces involve either the replacement or substantial modification of the existing equipment. Such modifications tend to be prohibitively expensive.
It is known that the fuel efficiency of a combustion furnace can be improved by using the heat in the furnace flue gases to preheat the combustion air used in the furnace. When the heat of the flue gases is recovered in this manner, the fossil fuel need only replace the heat energy lost through the actual heating of the furnace load and through the inefficiency of recovery of the flue gas heat.
In general, flue heat recovery apparatus may be classified as either "recuperators", or "regenerators". The two terms are not used consistently in the art, and are sometimes, in fact, used interchangeably. For the purposes of the present patent application, the term "regenerator" will be understood to refer to a system wherein the direction of flow of gases through the furnace is periodically reversed, whereas the term "recuperator" will be understood to refer to those systems wherein the recovery of heat from the flue gases is accomplished without the reversing of gas flow through the furnace.
Recuperators are simply heat exchangers which transfer heat energy from the POC to combustion air by conduction through a wall or walls which separates the two fluids. Regenerators, on the other hand, include two heat storage beds. Combustion air enters the furnace through one bed while the POC leave the furnace through the other bed. A reversing valve periodically reverses the direction of flow through the furnace and the beds.
Recuperators and regenerators are well known in the art, and are represented in the prior patent literature. Heat regeneration, in particular, has been widely used in connection with steel open-hearth furnaces and glass tanks since the middle 1800's.
Attempts have also been made to apply similar techniques to smaller installations, particularly those involving radiant tubes. Patents relating to such techniques include U.S. Pat. Nos. 2,399,609 and 4,355,973, and Great Britain Patent application No. 2,128,724.